The goal of this application is to characterize the protein dynamics of Hepatitis B virus (HBV) assembly, both in the capsid protein dimer and the assembled capsid of 120 HBV dimers, with the eye towards providing a new anti-viral therapeutic target. Specific Aim 1 of this application is to characterize the dynamics of the HBV capsid subunit. The HBV dimer interface has been shown to be critical for capsid assembly. We will use an intradimer disulfide at this interface as a marker for conformational change in the capsid subunit upon assembly. We will also investigate the effects of this disulfide on the kinetics of assembly in an effort to characterize the effects of this disulfide on the allosteric regulation of the disulfide. Understanding of the role of the dimer interface in capsid assembly may help to define it as a target for disrupting assembly in vivo. {Peptide} Specific Aim 2 of this application is to characterize capsid assembly dynamics by disruption of the assembly pathway with small molecules. We have a series of small molecules, the propenamides, that have been shown to affect capsid assembly. We will describe the mechanism of action of these molecules by observing their effects on the kinetics and thermodynamics of assembly. We will also visualize the products of the altered assembly reactions to determine the nature of any structural changes wrought by the propenamides and how they affect assembly. We then plan to determine the structure of the capsids in complex with the propenamides by either crystallography or cryo-EM image reconstruction. Identification of the mode of binding, the binding site, and the structural changes due to binding will serve to further our understanding of the structural changes associated with assembly as well as providing a starting point for antiviral drug design. PUBLIC HEALTH RELEVANCE: There are an estimated 400 million chronic cases of Hepatitis B worldwide;HBV is the leading cause of cirrhosis and hepatocellular carcinoma and is responsible for 1 million deaths per year. There is no reliable cure, and current antiviral treatments [tend to exploit a single target and as such] are giving rise to drug and vaccine resistant mutants. Characterization of the virus assembly pathway [and its role in viral maturation] may provide a new target for antiviral therapies.